Alfvén Wave Heating of the Solar Chromosphere: 1.5D Models

Abstract

Physical processes which may lead to solar chromospheric heating are analyzed using high-resolution 1.5D non-ideal MHD modelling. We demonstrate that it is possible to heat the chromospheric plasma by direct resistive dissipation of high-frequency Alfvén waves through Pedersen resistivity. However this is unlikely to be sufficient to balance radiative and conductive losses unless unrealistic field strengths or photospheric velocities are used. The precise heating profile is determined by the input driving spectrum since in 1.5D there is no possibility of Alfvén wave turbulence. The inclusion of the Hall term does not affect the heating rates. If plasma compressibility is taken into account, shocks are produced through the ponderomotive coupling of Alfvén waves to slow modes and shock heating dominates the resistive dissipation. In 1.5D shock coalescence amplifies the effects of shocks and for compressible simulations with realistic driver spectra the heating rate exceeds that required to match radiative and conductive losses. Thus while the heating rates for these 1.5D simulations are an overestimate they do show that ponderomotive coupling of Alfvén waves to sound waves is more important in chromospheric heating than Pedersen dissipation through ion-neutral collisions.

Propagation of Torsional Alfvén Waves from the Photosphere to the Corona: Reflection, Transmission, and Heating in Expanding Flux Tubes

“…It is of general consensus that the dissipation of high-frequency Alfvén waves might provide enough heating to compensate, at least partially, the radiative losses. Most of the existing works in the literature either follow a 0D local analysis in which spatial gradients are neglected and the wave equations are analytically solved locally at specific heights in the chromosphere (see, e.g., De Pontieu et al 2001;Song & Vasyliūnas 2011;Soler et al 2015a) or use a 1D model in which vertical spatial gradients are retained and wave propagation from the photosphere to the corona is numerically computed (see, e.g., Leake et al 2005;Goodman 2011;Tu & Song 2013;Arber et al 2016). A common feature of 1D models is that the expansion of the magnetic field is neglected, but this ingredient is very important in the solar atmosphere.…”

“…Indeed, observations suggest that Alfvénic-type waves can carry sufficient energy to heat the solar atmosphere and accelerate the solar wind (see, e.g., De Pontieu et al 2007;Tomczyk et al 2007;McIntosh et al 2011;Hahn & Savin 2014). However, there are still many open questions under debate, e.g., the source of excitation or driver of the waves (e.g., Fedun et al 2011a;Morton et al 2013;Mumford et al 2015), the reflection and transmission properties of the waves as they propagate through the various atmospheric layers (e.g., Hollweg 1978;Leroy 1980;Similon & Zargham 1992;Cranmer & van Ballegooijen 2005), the conversion and coupling between the different MHD wave modes (e.g., Hansen & Cally 2012;Khomenko & Cally 2012), and the physical mechanisms that may lead to the efficient dissipation of wave energy (e.g., Khodachenko et al 2004;Antolin & Shibata 2010;Goodman 2011;van Ballegooijen et al 2011;Tu & Song 2013;Soler et al 2015b;Arber et al 2016), to name a few.…”

Damping of Alfvén Waves by Turbulence and Its Consequences: From Cosmic-Ray Streaming to Launching Winds

“…The most well-known consequences of wave propagation and damping range from heating of coronal gas in Solar atmosphere (e.g. Arber, Brady & Shelyag 2016, Reep & Russell 2016, acceleration and scattering of cosmic rays (e.g. Jokipii 1966, Schlickeiser 2002, 2003, and launching of solar and stellar winds (e.g.…”

Explaining Inverted-Temperature Loops in the Quiet Solar Corona With Magnetohydrodynamic Wave-Mode Conversion

“…For example, instead of assuming the compressive waves are generated impulsively at the lower boundary, the models should include a self-consistent description of the height-dependence of plasma parameters in the chromosphere and TR, as well as the β-dependent physics of mode conversion (see also Cranmer & Woolsey 2015). Time-dependent simulations are beginning to show a broad diversity of mode coupling processes in this complex environment (Matsumoto & Suzuki 2014;Arber et al 2016). Lastly, our adopted rate of heating due to MHD turbulent cascade was a relatively simple phenomenological scaling law, but there are others (e.g., Rappazzo et al 2008;van Ballegooijen et al 2011;Asgari-Targhi et al 2013;Bourdin et al 2016) that may be more realistic.…”